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1. Detection of thin film phase transformations at high-pressure and high-temperature in a diamond anvil cell

   https://doi.org/10.1038/s43247-024-01234-9  

   Berrada, Meryem; Hu, Genzhi; Zhou, Dongyuan; Wang, Siheng; Nguyen, Phuong_Q H; Zhang, Dongzhou; Prakapenka, Vitali; Chariton, Stella; Chen, Bin; Li, Jie; et al (December 2024, Communications Earth & Environment)

   Abstract Quantifying how grain size and/or deviatoric stress impact (Mg,Fe)₂SiO₄phase stability is critical for advancing our understanding of subduction processes and deep-focus earthquakes. Here, we demonstrate that well-resolved X-ray diffraction patterns can be obtained on nano-grained thin films within laser-heated diamond anvil cells (DACs) at hydrostatic pressures up to 24 GPa and temperatures up to 2300 K. Combined with well-established literature processes for tuning thin film grain size, biaxial stress, and substrate identity, these results suggest that DAC-loaded thin films can be useful for determining how grain size, deviatoric stress, and/or the coexistence of other phases influence high-pressure phase stability. As such, this novel DAC-loaded thin film approach may find use in a variety of earth science, planetary science, solid-state physics, and materials science applications. 

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2. Intermolecular coupling and fluxional behavior of hydrogen in phase IV

   https://doi.org/10.1073/pnas.1916385116  

   Goncharov, Alexander F.; Chuvashova, Irina; Ji, Cheng; Mao, Ho-kwang (December 2019, Proceedings of the National Academy of Sciences)

   We performed Raman and infrared (IR) spectroscopy measurements of hydrogen at 295 K up to 280 GPa at an IR synchrotron facility of the Shanghai Synchrotron Radiation Facility (SSRF). To reach the highest pressure, hydrogen was loaded into toroidal diamond anvils with 30-μm central culet. The intermolecular coupling has been determined by concomitant measurements of the IR and Raman vibron modes. In phase IV, we find that the intermolecular coupling is much stronger in the graphenelike layer (G layer) of elongated molecules compared to the Br 2 -like layer (B layer) of shortened molecules and it increases with pressure much faster in the G layer compared to the B layer. These heterogeneous lattice dynamical properties are unique features of highly fluxional hydrogen phase IV. 

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3. Constraints on the viscosity of water at high pressures and temperatures using particle tracking analysis

   https://doi.org/10.1180/mgm.2026.10195  

   Ashley, Aaron Wolfgang; Mookherjee, Mainak (January 2026, Mineralogical Magazine)

   Abstract The viscosity (η) of a geofluid dictates its roles within the Earth, such as migration in subduction zones and volcanism. High pressures and temperatures at depth influence visocity (η). The falling sphere method is effective to measure viscosity at high-pressures for geofluids that form solids at ambient temperature. A typically metallic sphere is placed atop a solid sample, which is then compressed to high-pressure and later melted by heating. This method is more challenging for geofluids that do not form solids at ambient temperature. A diamond-anvil-cell (DAC) is often used to contain such geofluids, but requires a small sample chamber and that the sphere either falls parallel to the diamond culet faces or rolls along one face. This geometry produces complicated drag effects on a sphere fall and additional frictional forces for a roll. The sphere may also adhere to chamber surfaces, preventing its fall/roll. To circumvent these issues, in this study, we quantify the viscosity of a geofluid (H₂O) at pressures <2.5 GPa using the Brownian motions of suspended particles in DAC. Previous high-pressure efforts used particles of polystyrene, which are unstable at ≥300°C, or silica, but only at ambient temperatures. Such temperatures are relatively low for hydrothermal to supercritical geofluids. We tested quartz particles (∼1–2 µm diameter) with heating, as quartz does not significantly dissolve/melt until ≥600°C. Although three times denser than water, the particles remained suspended and displayed Brownian motions for long timescales at temperatures ≤200°C. The measured viscosities are relatively high due to drag from the culets and particle–particle interactions. Regardless, our measured pressure-effect on viscosity shows excellent agreement with the standard reference for water. After correcting for the drag, the η are very low (< 2 mPa s) highlighting that H₂O-rich geofluids should be highly mobile at depth. 

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4. Imaging stress and magnetism at high pressures using a nanoscale quantum sensor

   https://doi.org/10.1126/science.aaw4352  

   Hsieh, S.; Bhattacharyya, P.; Zu, C.; Mittiga, T.; Smart, T. J.; Machado, F.; Kobrin, B.; Höhn, T. O.; Rui, N. Z.; Kamrani, M.; et al (December 2019, Science)

   Pressure alters the physical, chemical, and electronic properties of matter. The diamond anvil cell enables tabletop experiments to investigate a diverse landscape of high-pressure phenomena. Here, we introduce and use a nanoscale sensing platform that integrates nitrogen-vacancy (NV) color centers directly into the culet of diamond anvils. We demonstrate the versatility of this platform by performing diffraction-limited imaging of both stress fields and magnetism as a function of pressure and temperature. We quantify all normal and shear stress components and demonstrate vector magnetic field imaging, enabling measurement of the pressure-driven α ↔ ϵ phase transition in iron and the complex pressure-temperature phase diagram of gadolinium. A complementary NV-sensing modality using noise spectroscopy enables the characterization of phase transitions even in the absence of static magnetic signatures. 

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5. Sub-micron circuit fabrication on diamond anvils for mesoscopic high-pressure experiments

   https://doi.org/10.1063/5.0253706  

   Rehfuss, Z R; Zheng, K; Gould, S L; Murch, K W; Ran, S (June 2025, Applied Physics Letters)

   We present a fabrication procedure to produce high-quality liftoff structures on diamond anvils that extend continuously from the culet onto the slanted facets. Feature sizes as small as 500 nm are achieved using a trilayer resist stack and electron beam lithography. Device structures with strong adhesion to the diamond surface and high abrasion resistance are realized by optimizing the surface treatment. To benchmark our process, we fabricate a multi-lead tungsten circuit to measure changes in the superconducting transition temperature of zirconium across the structural phase transition at ∼30 GPa, revealing a nearly fourfold increase in the critical temperature. Our process is reproducible in most traditional academic and industrial cleanroom facilities. This method enables reproducible, high-resolution circuit fabrication on diamond anvils and other faceted crystalline substrates. 

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